Visual inspection apparatuses, as examples of inspection equipment for visually checking whether parts are properly assembled to their designed positions of workpieces, are designed to carry out such visual checking using a camera attached to one end of a robot arm. An example of such visual inspection apparatuses is disclosed in Japanese Patent Application Publication No. H08-313225.
In such a visual inspection apparatus, a robot arm with one end to which a camera is attached is mounted at its base on, for example, the floor of a facility in which the visual inspection apparatus is installed.
When a workpiece is disposed at a preset check location in the facility, the visual inspection apparatus works to move the robot arm to thereby cause the robot arm to sequentially take target pickup poses in each of which an image of the workpiece is to be picked up by the camera.
The visual inspection apparatus also works to pick up an image in each of the target pickup poses, to process the picked-up images in the respective target pickup poses, and to carry out visual check of the workpiece based on the result of the image processing.
In the visual inspection apparatus, the target pickup poses in each of which an image of a workpiece is to be picked up by the camera have been taught to be stored in a memory of the visual inspection apparatus.
In order to determine such target pickup poses of a robot arm with one end to which a camera is attached, a teaching device is normally used. The teaching device is designed to be manually operable and to remotely access a controller of the robot arm to thereby instruct the controller to move the robot arm to desired locations.
Specifically, a user manually operates the teaching device to instruct the controller to move the robot arm while monitoring images of a workpiece disposed at the check location; these images are sequentially picked up by the camera in different pickup poses and sequentially displayed on a display device.
When determining that an image of the workpiece picked up by the camera located in a pickup pose is a desired image for visual check of the workpiece, the user operates the teaching device to store therein the pickup pose as a target pickup pose.
On the other hand, U.S. Pat. No. 6,542,922 corresponding to Japanese Patent Application Publication No. H11-242513 discloses a technique for determining a target location of a robot in simulations; this technique will be referred to as “simulation technique” hereinafter.
Specifically, in order to improve the efficiency of determining the target location of the robot, the simulation technique is designed to estimate a virtual spherical object and a virtual camera on the surface of the virtual spherical object.
The simulation technique also virtually moves the virtual camera on the surface of the virtual spherical object in the directions of: the equator of the virtual spherical object, the polar orbit of the virtual spherical object; and the radius thereof to thereby display a tangent plane including one end of the robot arm to which an end effector is attachable.
This easily determines the target location for the one end of the robot arm within the tangent plane.